With continuous development of science and technology, a mobile phone can realize more and more functions. In addition to a call function, the mobile phone may be used for accessing Internet, watching video, reading e-books and so on. A size of a display screen of the mobile phone directly affects user's experience on the above functions. For example, in the case that the mobile phone is used for watching video, the bigger the display screen is, the better the user's experience is. However, in the case that the mobile phone is used for calling, the size of the display screen is no longer so important to the user. At present, the size of the display screen of the mobile phone keeps constant, which cannot be adjusted by the user according to actual situations, so that flexibility of using the mobile phone is reduced.